The present invention concerns a syringe for medical use, and more precisely a disposable syringe with protected needle.
It is known that the syringes of said type essentially comprise a hollow body, said body having a cylindrical shape with one end open, the other end being tapered and having such a shape as to receive a normal needle for injections. Within the cylindrical body a tight sealing piston can be moved in both directions, said pistons being driven by means of a stem that projects out of said open end of the cylindrical body.
At the moment of sale, the syringe needle is normally protected by means of a cap to be removed before using the syringe.
These syringes have the cylindrical body, stem and cap made of a substantially stiff synthetic material, the piston being on the contrary made of rubber or a resilient synthetic material having a suitable hardness. The syringe is employed in the following known way.
After removing the needle protection cap by grasping with the fingers the tip of the stem, the piston is shifted away from its position by the needle, or terminal position, in which the piston normally is at the moment the syringe is purchased. This displacement causes a depression to arise inside the syringe, by means of which, from a vial or ampoule, the proper amount of liquid drug is sucked through the needle.
Thereafter, the injection is performed in the usual known way. The needle protection cap is finally put on again before disposing of the whole assembly.
The low-cost syringes made of synthetic material are normally used only once, and then disposed off. This is due to obvious hygienic reasons that have become even more stringent, nowadays, mainly due to the diffusion of AIDS (acquired immuno-deficiency syndrome), one of the best transmission vehicles for which is indeed the used syringe.
It is however evident, that the protection cap can be easily removed, for example by children that might find said used syringes, or can be pulled-out accidentally during the transportation of waste into which the syringes are normally thrown with the serious troubles this can cause.